Branching filter capable of demultiplexing electric signals having different frequencies in accordance with the frequencies are widely used for antenna duplexers of communication apparatuses and the like. For example, a branching filter is known that has a configuration in which an input terminal and a first output terminal are connected through a low-pass filter and the input terminal and a second output terminal are connected through a high-pass filter and that has a function of outputting an electric signal having a first frequency band, which is a lower frequency band, from the first output terminal through the low-pass filter and outputting an electric signal having a second frequency band, which is a higher frequency band, from the second output terminal through the high-pass filter (for example, refer to PTL 1). In a conventional branching filter proposed in PTL 1, phase-shift circuits are inserted between the input terminal and the low-pass filter and between the input terminal and the high-pass filter. These phase-shift circuits cause impedance at a time when the second output terminal is viewed from the input terminal and cause impedance at a time when the first output terminal is viewed from the input terminal to be close to infinity in the first frequency band and in the second frequency band, respectively. In doing so, leakage of electric signals having the first frequency band from the second output terminal and leakage of electric signals having the second frequency band from the first output terminal are prevented.